Steel manufacture



Patented Feb. 9, 1926.

THOMAS J. BRAY, n or ionnes'rown, OHIO.

s'rnm. IAHUIACTUBE.

Io Drawing.

To all whom it may cmwem:

' a citizen of the United States, and a resident mg furnace, resulting State of Ohio,

of Youngstown, county of Mahoning, and have invented a new and useful Improvement in Steel Manufacture, of which the following is a specification, the principle of the invention being herein ex plained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

It is, of course, well understood that the manufacture of steel involves the oxidizetion of impurities existing in the raw materials and the removal of the products of such oxidization either in the slag or as a gas. The finalst'age in such process of manufacture requires the removal of the resulting excess of oxygen in the steel, this being accomplished by correct methods of operation ofthe furnace or converter and by the addition of a (leoxidizer, such as manganese, silicon or aluminum, to the molten steel. .Such deoxidizer is sometimes added to the steel bath in the furnace or it may be thrown into the ladle as the metal is tapped from the furnace or poured from the converter. If sufliciently deoxidized the steel, when turned into the molds, will solidify quietly, i. e.. without'the evolution of gas, and is then known as killed steel, but if incompletely deoxidized, it will solidify with the evolution of large volumes of gas and is then known as efiervescing or rimmed-in steel. For many puposes such eflervescing or rimmed-in steel is to be preferred to killed steel, but its manufacture has heretofore been attended with some dif ficulties which it is the purpose of the present invention to overcome.

Briefly stated, steel, an ample supply of carbon-monoxide or carbon-dioxide gas must be left in the steel so as to give a vigorous boiling action in the molds. This action should commence immediately after the ingot is poured for if it does not. the ingots will have a Weak structure, gas holes will be located close to the surface and a defective product will result. Thus ingots produced underthe conditions stated tend to crack in the rolling mill and the skin blow-holes become oxidized on their interior surfaces in the heatin a scabby surface on the finished product.

formation of blow-holes.

in making efiervescing Application filed nine 5, 1m. Serihl No. 586,152.

-When the evolution of gas from effervescing steel is'delayed to a certain extent, the steel rises or rows in the molds as it solidifies, this Eeing probably due to the pro ressively increasing boiling action and to t e displacement of the liquid metal by This phenomenon may be attributed to two neither of which is under absolute control, viz, temperature and degree of deoxidization. .Other conditions being equal, the higher the temperature of the steel as it is tapped and poured, the greater the tendency to delayed gas evolution in the molds. This is shown by the fact that the best effervesc= ing steel is made when a small skull is left in the steel ladle; In the matter of deoxidization, ifthe steel is too thoroughly deoxidized, the carbonaceous gases are decomposed and an insufficient supply is left inth" steel to give the desired rate of evolution in the molds. Since over-oxidized steel is just as bad, if not worse, than-under-oxidized steel, the desired degree of deoxidization is difficult to obtain, the difliculty being aggravated by the fact that most of the deoxidization must be done in the melting furnace. for best results in order that the solid, non-metallic products may separate readily from the steel. A direct effect of the aforesaid growing action is a spongy top on the ingot which must be cut off in the roll ing mill as crop and is a direct loss.

The object of the present invention, accordingly, is to enable the steel maker to pour his metal at a temperature high enough to pour cleanly and to afford maximum separation of impurities, as well as to deoxidize suificiently in the furnace, by proper slag manipulation and proper additions of deoxidizing agents, to insure against the presence of an injurious excess of oxygen, while yet obtaining at the same time a vlgorous boiling or rimming action in the molds. Such action I. have found can be secured by the introduction of carhon-dioxide gas, or ingredients capable of directly giving ofi such gas, into the steel as it runs into the ladles or molds. Specifically-I have found that by thus introducing a relatively small amount of sodium car nate or soda ash, as it is commercially known, (Na Co e. g., one-half pound per ton of steel, an ample amount of such gas is released in most cases to produce the desired principal causes,

into carbon-dioxide and a metallic oxide as per the following equation Na3CO3 Nfl-gO CO:-

The direct effect of the addition of the gas is shown in the appearance of the SOlIdifying ingot. Growing in the molds 1511i)- solutely eliminated; surface blow-holes, if not eliminated entirely, are located much further toward the center; and surface defects in the product are accordingly cut down to a large extent. The product con tains fewer seams, slivers, scabs and blisters, and due to the more solid top obtained, less material requires to be discarded while passinn the ingot through the rolling mill.

' t should be noted that sodium oxide is valuable as a flux and aids inthe purification of the steel by lowering the melting point of any solid impurities present, causing them to separate more readily. As a matter of fact, however, it is probable that the bulk of such oxide is volatilized at the temperature of the molten steel and passes off. It may be a question whether the gas is retained in the steel in the form of the carbon-dioxide indicated by the foregoing equation or whether it is partly reduced to the monoxide form by the carbon or manganese present in the steel; but in any case it can be stated that no appreciable reduction in the above elements is occasioned by the addition of the small amount of soda ash indicated,.viz, one-half pound per ton of steel.

Other modes of; applying the principle of my invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or stepsbe employed.

'1. n the manufacture of steel, the ste wvhich consist in suitably deoxidizing tie same in the furnace, and then producing an artificial efi'ervescence throughout the body of molten steel immediately following the pouring of the same into the mold, substantially as described.

2. In the liianufacture of steel, the ste s which consist in suitably deoxidizing t e samein the furnace and then engendering an oxide of carbon in gaseous form throughout the body of molten steel incidentally to the transfer of the same from the furnace into the mold, whereby an artificial effervescence is produced immediately following such transfer.

3. In the manufacture of steel, the ste s which consist in suitably deoxidizing tlie same in the furnace, and then intermixing with the molten steel incidentally to the transfer of the same from the furnace into the mold a compound capable of generating an oxide of carbon gas, whereby an artificial effervescence is immediately produced throughout the body of metal in the mold.

4. In the manufacture of steel, the ste s which consist in suitably deoxidizing t 0 same in the furnace and then intermixing with the molten steel incidentally to the transfer of the same from the furnace into the mold a relatively small quantity of an alkali metal carbonate.

5. In the manufacture of steel, the ste s which consist in suitably deoxidizing the same in the furnace and then intermixing with the molten steel incidentally to the transfer of the same from the furnace into tllle mold a relatively small quantity of sodaas 1.

6. In the manufacture of steel, the ste s which consist in suitably deoxidizing tie same in the furnace and then intermixing with the molten steel incidentally to the transfer of the same from the furnace into the mold a relatively small quantityof sodaash in approximately the ratio of one-half pound thereof to one ton of steel.

Signed by me this 31st day of May', 1922.

' THOMAS J. BRAY, JR. 

